Clues: Mr. Birdy and his Parts

1. I am strong and thick and can really do the trick, especially with a lot of grit.
2. Millions of barbs on every vane, without me winter would be a pain.
3. My shape gives birds something really neat: a lift to get them off their feet.
4. Space inside to keep me light, struts that brace to give me might.
5. I am not a friend of water - that is a fact. And I am a big part of the preening act.
6. Two small holes are the only clues that we are inside a bird, hidden from view.
7. Depending on what a bird might eat, I can double my size — that is quite a feat!
8. In some birds we are found almost everywhere. We are hooked to the lungs and filled up with air.